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Old 09-13-2017, 09:17 PM   #1
cookieboy
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Default Would just a thicker front sway bar make a difference ?

So as some of you know, I'm hoping to find another white 240 in the near future and when I gave my previous one to my stepson, I also gave him the 23 mm front sway bar that was never installed. He said I can have it back to put on the next one since he never used it and I was wondering if it will help flatten the handling in the curves or would I also need a thicker rear one ? I'm just trying to map out my game plan for the possible future, thanks.
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Old 09-13-2017, 09:50 PM   #2
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Yes, just a thicker front one will still help.
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Old 09-13-2017, 10:40 PM   #3
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Ideally you will want no bar in the rear or as little bar as possible to keep the axle from binding.
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Old 09-13-2017, 11:03 PM   #4
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I have 25mm up front and no rear bar in the back
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Old 09-13-2017, 11:15 PM   #5
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I have 25mm up front and no rear bar in the back
Ditto
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Old 09-13-2017, 11:50 PM   #6
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23mm in the front for me and as recommended here I stayed with the stock skinny bar (16mm?) on the rear of my '89 245. For me it made the steering sunburn sensitive and the lagging response of the rear just felt wonky to me. 21mm rear bar made it feel much more stable. YMMV.
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Old 09-14-2017, 07:14 AM   #7
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Stiff front and soft rear = understeer more.

Is that what you're looking for?
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Old 09-14-2017, 08:18 AM   #8
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Ideally you will want no bar in the rear or as little bar as possible to keep the axle from binding.
And ideally no front bar either if you are on surfaces that need good wheel articulation.
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Old 09-14-2017, 08:20 AM   #9
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23mm in the front for me and as recommended here I stayed with the stock skinny bar (16mm?) on the rear of my '89 245. For me it made the steering sunburn sensitive and the lagging response of the rear just felt wonky to me. 21mm rear bar made it feel much more stable. YMMV.
You are about spot on there. The rear bar wants to be a touch smaller for good balance in handling. Too big a variation will make the car unpredictable on the road
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Old 09-14-2017, 08:38 AM   #10
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You are about spot on there. The rear bar wants to be a touch smaller for good balance in handling. Too big a variation will make the car unpredictable on the road
is that why volvo offered a 25mm rear bar in their r sport catalogue?
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Old 09-14-2017, 04:55 PM   #11
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Originally Posted by tryingbe View Post
Stiff front and soft rear = understeer more.

Is that what you're looking for?
I was just looking to have a car was was flatter in the curves. Perhaps if the time comes, I'll need to find a thicker rear bar all.
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Old 09-14-2017, 05:12 PM   #12
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And ideally no front bar either if you are on surfaces that need good wheel articulation.
Key difference is that the front can still articulate well enough on pavement with a stiff bar whereas the axle,(which relies on bushing compliance to achieve torsional rotation) does not.
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Old 09-15-2017, 05:30 AM   #13
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You are about spot on there. The rear bar wants to be a touch smaller for good balance in handling. Too big a variation will make the car unpredictable on the road
Are you speaking from experience or just repeating something you heard? I've had mine at track speeds with no rear bar, I'm not sure what you're talking about.
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Old 09-15-2017, 06:57 AM   #14
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From lots of experiance and many many cars. An example of this is when converting from nivo shocks to normal springs and dampers the back end becomes very unstable. Even with stiffer rear springs this is still the case and most noticable with estates. You get the same kind of problem if only fitting a front IPD bar. I also found if fitting a full set of IPD bars combined with soft springs does not work well either.
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Old 09-15-2017, 07:00 AM   #15
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Key difference is that the front can still articulate well enough on pavement with a stiff bar whereas the axle,(which relies on bushing compliance to achieve torsional rotation) does not.
No the key difference is the front wheels are indipendant as where the rear wheels are stuck to each other via the axle. Even so in most cases you only want a little more front bar compared to rear unless perhaps your spring rates are a way off. Again how you use the car will effect this
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Old 09-15-2017, 09:04 AM   #16
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I remember when I was installing the (stiff) set of IPD bars on my PV. I did the rear bar first, and took it for a quick spin with that on and no front bar. Lol, it almost *was* a spin, it was pretty prone to oversteer. More fun than I need in my life.

Put the front bar on and now it is very nicely balanced between under and over steer, you can coax it into either one.

Roll bars do two things, one is the more noticeable (if you're not going to and past the limit of adhesion) - simply making the car lean less in corners.

The second involves the roll stiffness balance between the front and rear, which is a combination of the spring rates (and shock valving in a quick transition) and the roll bar stiffness. Generally speaking - the end with the greater roll resistance/stiffness will be the end that breaks loose first. Again, in very general terms, the reason Volvo generally tended to put front bars on and not always rears is to ensure that the cars had a fair amount of understeer from the factory - understeer being what is safer for drivers on public roads. The tail coming around in a corner on an unsuspecting driver is a very bad thing, it's not great on a suspecting driver either. The car just plowing straight ahead scrubbing the front wheels is a lot safer for all involved.

If you're not worried about which end will break loose, or if you don't care that there's a fair amount of understeer, just go with a nice stiff front bar. Getting the balance closer will allow you to go around corners a little faster, but only if you're hustling it at 9/10ths or more, at or close to the limit of adhesion.

Also, I don't think you can compare the thicknesses of the front and rear bars directly, because on a 240 at least, they operate in different manners. The front acts directly between the lower control arms and the front subframe, the rear just ties the two lower control arms together. You'd have to ponder the geometry between the two methods to determine what the diameters really mean in relation to each other.

I don't think IPD did any sort of complicated maths like that, they probably just tried out a bunch of different combinations and drove the test car around a track, and figured out which combination leads to a nice balance with just a small amount of understeer.
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Old 09-15-2017, 09:25 AM   #17
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I was just looking to have a car was was flatter in the curves. Perhaps if the time comes, I'll need to find a thicker rear bar all.
A thick front bar will give you flatter in the curve, but it will not help you to get faster corner speed.

If you're ok with that, get it. But, you can always double up stock sway bars and save some $$$.

http://forums.turbobricks.com/showthread.php?t=9587
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Old 09-15-2017, 10:06 AM   #18
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It's not appropriate to suggest no rear bar unless you know what sort of spring rate being run in the rear. Assuming roll stiffness is only a factor of the anti roll bar is incorrect. Sure if you're running a high spring rate in the rear it is probably appropriate to run no ARB. Nothing is black and white.
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Old 09-15-2017, 10:11 AM   #19
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Swaybar threads are the new oil threads.
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Old 09-15-2017, 10:34 AM   #20
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Homer, agree fully with you there.

John also agree with you to a fair extent but a do prefer the rear to go first over front pushing forward. Ideally all four wheels should start to loose grip at the same time.
Anti roll bars are more fine tuning and you do need to get the balance front to rear about right.
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Old 09-15-2017, 10:48 AM   #21
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I like a balance too, I was just saying why Volvo put the cars out with a hefty amount of understeer backed in.
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Old 09-15-2017, 11:45 AM   #22
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Anti-sway bars should be a final "tune" of sorts when you're addressing the way a car handles. Once you get the geometry and compression/rebound set to your liking/driving taste/type of driving; then you move to the sway bars. Utilize the suspension to get it a nearly set or set. Then a sway bar to tighten(for lack of better words) up the cornering. Take a look at rally cars, they have a long suspension travel, yet corner quite flat. It has to do with the initial suspension set up. Derail complete.
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Old 09-15-2017, 02:46 PM   #23
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I'm so glad you guys talked about this. I've had a couple scary situations (no autoX yet) where I've gone into corners hard and found the rear end swinging round hard and the front heading straight into the corner just as JohnMc describes... so basically it sounds like I have some pretty decent oversteer with my setup.

I have a 25mm/25mm front/rear bars on the car right now and I guess because of my oversteer I'm looking to decrease the rear bar size or go without a rear bar. Do you guys know if anyone makes/made a rear bar that had dual exhaust cutouts aside from the ipd 25mm unit?
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Old 09-15-2017, 02:52 PM   #24
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Might check other variables first.

Tires the same on all 4 corners? What about the pressure? Lower pressure in the rear might not reduce actual grip all that much (unless it's really low), but in a quick transition a lower pressure can let the rear deflect a bit more, which starts that end of the car moving a little, which can continue on into a loss of traction. Shocks can also do things like that in a quick transition in a way that wouldn't happen if you eased into the corner.
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Old 09-15-2017, 03:02 PM   #25
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I'm so glad you guys talked about this. I've had a couple scary situations (no autoX yet) where I've gone into corners hard and found the rear end swinging round hard and the front heading straight into the corner just as JohnMc describes... so basically it sounds like I have some pretty decent oversteer with my setup.

I have a 25mm/25mm front/rear bars on the car right now and I guess because of my oversteer I'm looking to decrease the rear bar size or go without a rear bar. Do you guys know if anyone makes/made a rear bar that had dual exhaust cutouts aside from the ipd 25mm unit?

Using the 25/25 should give you more oversteer but what you are describing is understeer and a twitchy rear. What springs are you running? It could be the front springs are too soft
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